Larger social networks and/or more frequent social interactions are associated with lower incidence of AD, at the population level; increasing social interaction may be a promising intervention for improving the cognitive well-being of older adults. In our previous randomized controlled behavioral clinical trial, we developed a conversation-based social interaction cognitive stimulation protocol delivered by trained interviewers through personal computers, webcams, and a user-friendly interactive Internet interface with a touch screen (ClinicalTrials.gov:NCT01571427). Daily 30-minute face-to-face communications were conducted over a 6- week trial period in the intervention group. Despite a small sample size, this pilot study (completed 6/30/2014) demonstrated feasibility, high adherence in an elderly population (mean age 80 years) and efficacy in language-based executive functions among the intervention group in comparison to the control group. Based upon these positive results, we propose a Phase I trial to advance development of this intervention. Primary aim (Aim 1) is to examine the efficacy of our intervention on cognitive functions among the target group - those aged 80 and older with MCI and limited opportunities of social interactions. Our primary outcomes are cognitive functions in the domains of language, attention, executive and memory functions, and secondary outcomes are a targeted IADL function (medication use and adherence) and overall emotional well-being (mood, self-rated health). Person-specific levels of social interactions (i.e., average conversation outside of the trial) will be monitored and controlled in the analyses. Exploratory Aim 2 is to examine whether the intervention could lead to changes in speech and language characteristics over time by analyzing recorded daily conversational sessions, based on our promising cross-sectional findings in this area. Exploratory Aim 3 is to examine underlying mechanisms of efficacy by assessing pre- and post- trial changes inhippocampal, dorsolateral prefrontal cortex, amygdala and other ROIsusing MRI and unbiased whole brain assessment (voxel-based morphometry), and structural and functional connectivity using diffusion tensor imaging (DTI) and resting state functional MRI (R-fMRI). A total of 144 MCI subjects will be recruited and randomized at Portland, Oregon, and Detroit, Michigan, collaborating with Meals on Wheels and Area Agency on Aging (AAA) at both locations, creating a large sampling frame of those with low income and from ethnic minorities. Half of the participants will be randomly selected and invited to participate in the brain imaging study. Increasing daily social contact through communication technologies could offer a cost-effective home- based prevention that could slow cognitive decline, delay the onset of AD, and thereby reduce the overall societal burden of dementia. The oldest old is the fastest growing segment of the population in most developed countries, and face the highest risk of developing dementia and social isolation (risk factors of adverse health outcomes). User-friendly sustainable prevention approaches are urgently needed in this population.